Diagnosis of Colon Cancer

Screening And Diagnosis Of Colon Cancer

Screening tests help find polyps or cancer before you having symptoms. Finding and removing polyps may prevent colorectal cancer. Treatment for colorectal cancer is more likely to be effective when the disease is found early. Persons with high or moderate risk of colorectal cancer should be screened. The following screening tests can be used to detect polyps, cancer, or other abnormal areas:
  • Fecal occult blood test (FOBT): Sometimes cancers or polyps bleed, and the FOBT can detect tiny amounts of blood in the stool. If this test detects blood, other tests are needed to find the source of the blood.
  • Cologuard: A stool-based colorectal screening test that detects the presence of red blood cells and DNA mutations that may indicate the presence of certain kinds of abnormal growths that may be cancers. Patients with positive test results are advised to undergo a diagnostic colonoscopy.
  • Sigmoidoscopy: Rectum and the lower part of the colon are checked with a lighted tube called a sigmoidoscope. Polyps found are removed. The procedure to remove polyps is called a polypectomy.
  • Colonoscopy: The inside of the rectum and entire colon are examined using a long, lighted tube called a colonoscope. Polyps found are removed. A biopsy is done if an abnormal tissue is found inside the colon.
  • Double-contrast barium enema: An enema with a barium solution is given and air is pumped into the rectum. Several x-ray pictures are taken of the colon and rectum. Polyps or tumors may show up. This procedure is considered if someone is unable to undergo a colonoscopy. If an abnormality is detected by barium enema, then a colonoscopy is needed to either remove it or to do a biopsy.
  • Digital rectal exam: A rectal exam is often part of a routine physical examination. A lubricated, gloved finger is inserted into your rectum to feel for abnormal areas and detect any blood in the stool
If tests results show an abnormal area, such as a polyp, a biopsy to check for cancer cells may be necessary. Often, the abnormal tissue can be removed during colonoscopy or sigmoidoscopy. A pathologist checks the tissue for cancer cells using a microscope.

Colon Cancer Symptoms

The most commonly observed symptoms include—
  • Having diarrhea or constipation
  • Feeling that your bowel does not empty completely
  • Finding blood (either bright red or very dark) in your stool
  • Finding your stools are narrower than usual
  • Frequently having gas pains or cramps, or feeling full or bloated
  • Losing weight with no known reason
  • Feeling very tired all the time
  • Having nausea or vomiting
However, colon cancer in early stages may not produce any symptoms; this is why screening for colon cancer is necessary to detect cancer at an early stage.


As soon as the colon cancer is diagnosed, it is important to know the extent (stage) of the disease to plan the best treatment for the cancer. The stage is based on whether the tumor has invaded nearby tissues, whether the cancer has spread and, if so, to what parts of the body. Some of the following tests may be done to find out the stage of the cancer;
  • Colonoscopy: If colonoscopy was not performed for diagnosis, it is done to find the extent of the disease.
  • Endorectal ultrasound: An ultrasound probe is inserted into the rectum. The probe sends out sound waves that people cannot hear. The waves bounce off the rectum and nearby tissues, and a computer uses the echoes to create a picture. The picture may show how deep a rectal tumor has grown or whether the cancer has spread to lymph nodes or other nearby tissues.
  • Chest x-ray: X-rays of chest may show whether cancer has spread to the lungs.
  • CT scan: An x-ray machine linked to a computer takes a series of detailed pictures of areas inside your body. You may receive an injection of dye. A CT scan may show whether cancer has spread to the liver, lungs, or other organs.
The following stages of colorectal cancer are described:
  • Stage 0: The cancer is found only in the innermost lining of the colon or rectum. Carcinoma in situ is another name for Stage 0 colorectal cancer.
  • Stage I: The tumor has grown into the inner wall of the colon or rectum. The tumor has not grown through the wall.
  • Stage II: The tumor extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
  • Stage III: The cancer has spread to nearby lymph nodes, but not to other parts of the body.
  • Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs.
  • Recurrence: This is cancer that has been treated and has returned after a period of time when the cancer could not be detected. The disease may return in the colon or rectum, or in another part of the body.